Analog and digital valves are well known. Generally, analog valves regulate flow by opening or closing a valve gate until the desired flow rate is realized. Some analog valves can be adjusted manually by turning a valve stem. Other analog valves can be adjusted automatically by electric, pneumatic, or hydraulic actuators that can open or close the valve gates using sensors which detect the valve gate position.
Unfortunately, analog valves have limitations that can be problematic in many valve applications. For example, mechanical clearances, friction in valve linkages, fluid forces acting on the valve gate and stem can result in uncertainty in the valve setting and can result in unpredictable fluid flow when changes in the valve are made. Additionally, analog valves can be too slow in making changes to fluid flow conditions for rapid response applications such as hydraulic actuators.
Digital valves seek to overcome the deficiencies of analog valves. For example, some digital valves regulate fluid flow with a series of valves having electronic gates operated independently by an electrical signal. Each valve can be opened or closed very quickly to increase or decrease fluid flow by the number of valves that are open. Thus, a flow rate can be achieved by opening the proper valve or combination of valves. A control system, such as a computer or the like, can be used to control the flow rate.
Unfortunately, many digital valves have limitations that can be problematic in many valve applications. For example, complex fluid systems can have fluid flow forces, mechanical interactions, and electrical forces that affect the fluid flow stream control accuracy. Additionally, these forces can make it hard to proportionally control fluid flow from typical digital valves. For example, high pressure hydraulic fluid in a miniature hydraulic system can interfere with valve linkages and gates such that the gates cannot be closed to affect a proportional fluid flow.